Let us suppose that an aircraft pilot wishes to go by air from a first point to a second point and that a crosswind is blowing on the route that the pilot will have to take to connect these two points. The pilot will have to apply a correction to the path of his aircraft in order to take account of the crosswind; otherwise he will drift off his route and will be unable to reach his destination point.
In order to calculate this path correction, the pilot currently has available a nomogram or abacus type navigation instrument well known in the aeronautics field. This navigational aid takes the form of an assembly of three concentric superposed discs able to be rotated in relation to each other and to which data is added relating to the speed of the aircraft, the true magnetic heading, the crosswind value and the angular correction to be made to the aircraft's path. On the upper disc which is transparent, a nomogram used for effecting a part of the path correction calculation is provided.
The aircraft pilot, like the navigator, thus has an instrument that allows him, via a certain number of readings of numbered indications and calculations, to determine the heading correction to apply in order to take account of a crosswind. It is clear, of course, that the pilot or sailor must have this instrument permanently to hand. However, this instrument can easily be lost among the numerous charts, official documents and other items that the pilot or sailor has to carry with him. Moreover, this navigational instrument is conventional made of cardboard. It can thus become dirty and worn.
It is an object of the present invention to overcome the aforementioned drawbacks in addition to others by providing a timepiece associated with a nomogram type navigation instrument as described above.